Conventionally, it is known practice to provide light-metal parts, in particular aluminum components, which are used in large quantities in aircraft construction, with a protective layer by means of anodization. During chromic acid anodization (CAA=Chromatic Acid Anodizing), a protective layer which can be visually detected in a simple manner is produced, said layer having a “grey” appearance, while the surface of parts which have not been anodized have a “shiny” appearance. However, for reasons of better environmental compatibility, it is desirable to anodize parts of the type mentioned in another manner. An alternative anodization method is the TSA (Tartaric-Sulphuric Acid) method. As regards the corrosion protection required, this method is at least equal to the abovementioned chromic acid anodization but the layer formed cannot be visually detected.